Hook for actuating pull up hitch

ABSTRACT

A stanchion is provided with a latch system which is operable from the tractor which positions the trailers such that a gate on the tractor locks and unlocks the latch to appropriately reposition the stanchion during the positioning of the trailer. The tractor also includes a hook which engages the stand to raise the stand during loading of the trailer from its lowered to its raised position to engage and secure the tractor and also to reposition the unlocked stand during unloading of the trailer.

This is a Continuation of application Ser. No. 07/984,566 filed Oct. 4,1993, now U.S. Pat. No. 5,462,394 corresponding to PCT/US91/06576 filedSep. 12, 1991 which is a continuation-in-part of U.S. patent applicationSer. No. 07/581,328 filed Sep. 12, 1990 and now U.S. Pat. No. 5,112,172.

TECHNICAL FIELD

The present invention relates generally to supports for trailers onrailroad cars and more specifically to an improved stanchion to supporttrailers on railroad cars.

BACKGROUND ART

It is well known to transport trailers of trucks on railroad cars,namely, flat bed railroad cars. Some designs have used specializedstructure railroad cars and adapters for the landing gear ofsemi-trailer trucks as illustrated in U.S. Pat. No. 2,864,321. Othershave provided stands for the king pin of the trailer which ride along apair of slots in the surface of the railroad car, and generally includea manually actuated mechanism to hold the stand in place on the carafter adjustment. Examples of these structures are shown in U.S. Pat.Nos. 2,845,878; 2,846,172 and 2,903,977.

Collapsible fifth wheel stands have also been installed at one end of aflat bed and arranged to be raised by a chain pulled by a truck tractorbeneath a parked trailer to secure it to the railroad car. This is shownin U.S. Pat. No. 3,202,390. Examples of stationary, collapsible fifthwheel stands which are raised or lowered by spring, screws or hydraulicinclude U.S. Pat. Nos. 3,180,282; 3,189,307; 3,291,074 and 3,289,987.

A self-propelled stanchion which can be positioned along the surface ofthe railroad car and raised and lowered using internal or externalmotors is described in my U.S. Pat. No. 4,718,800. But its operation wasindependent of the trailer positioning.

All of the systems of the prior art have advantages and disadvantages.Those which use specialized car design are not usable to transport othertypes of freight. Those which have erect stand are not as storable andrequire the removal of unused stands at one location and a supply at theunloading location if there is further loading to be performed. Some ofthe collapsible stands are not adjustable along the surface of the flatbed and, thus, do not allow for optimum placement of the maximum numberof trailers on a train system. The positioning and securing of thestanchions require special equipment or more than one operator or pluralsteps in addition to positioning connecting and disconnecting thetrailer.

Thus, it is an object of the present invention to provide a stanchionwhich is adjustable along the surface of a railroad car.

Another object of the present invention is to provide a stanchion systemwhich reduces the number of steps in loading, securing, unsecuring andunloading a trailer on and from a railroad car.

Still another object of the present invention is to provide a systemwherein the stanchion is repositioned and operated from the tractorwhich positions the trailer.

These and other objects of the invention are obtained by providing astanchion with a latch system which is operable from the tractor whichpositions the trailer such that the tractor locks and unlocks the latchto appropriately reposition the stanchion during the positioning of thetrailer. The stanchion includes a sled to which a stand is mounted. Thelatch is biased to be normally engaged to the rail car to preventmovement of the sled, and in response to an external force from thetractor disengages the rail car to prevent movement of the sled. Thelatch includes at least one dog and an operator or piston moving thedogs to disengage a railroad car in response to an external force. Theoperator and dogs are biased to the engaging position. The sled includesa channel which receives a horizontal portion of a track and the dogsengage the vertical portion of the track. The track includes a pluralityof apertures in which the dogs are received.

An interlock is provided between the latch and the stand for permittingthe latch to disengage from the railroad car only when the stand is inthe lowered position. The interlock includes a cam connected to thelatch and having a camming surface which has a first and secondpositions corresponding to the lock and unlocked position of the latch.A cam follower is connected to the stand for at least engaging the camsurface in the second position when the stand is in the loweredposition. The cam follower disengages the cam surface in the firstposition when the stand is not in the raised position.

The tractor includes a gate having a locking and unlocking position. Inthe unlocking position, the gate engages the operator of the latch whenthe tractor is adjacent to the sled to apply the external force tounlock the latch. In the locking position, the gate does not apply theexternal force to the latch when the tractor is adjacent to the sled.The tractor also includes a hook which engages the stand for twopurposes. First it is used during loading of the trailer to raise thestand of a latched or locked sled from its lowered to its raisedposition to engage and secure the tractor. Second, when the stand is inits lowered position and the tractor's unlocking gate is in its unlockposition the hook engages the stand and prevents motion of the sled awayfrom the adjacent tractor. With the sled and stand thus captured betweenthe hook and the gate, any movement of the tractor in either forward orreverse direction, will be transmitted to the unlocked sled, and it willthus move with the tractor and be repositioned during the loading andunloading of the trailer by the tractor.

The hook may be a single element manipulated by an operator or may be apair of links pivotally connected and moved between an extended andretracted position by an operator in combination with a third link. Thehook is mounted on a slide block to the tractor, and a shock absorber isprovided. This increases the ability to move the hook while the stand isin the raised position. The hook includes first and second memberspivotally connected together to form the hook. A lock is provided havinga first position for locking the first and second members into a hookconfiguration and a second position to allow first and second members torotate relative to each other. Thus, when the hook is unlocked, theforward motion of the tractor relative to the stand will cause the twomembers to rotate relative to each other and release the hookconfiguration and the hook from the stand. Biasing means such as aspring is provided for biasing the first and second members into thehook configuration.

A method of loading and securing a trailer to the railroad car using thetractor includes positioning the trailer over a lowered stanchion on thesurface of the railroad car. The trailer and stanchion are thenrepositioned to a desired position on the surface of the railroad carusing the tractor. The tractor is disconnected from the trailer and thestanchion is raised by the tractor to connect and secure the trailer tothe railroad car. Apparatus on the tractor as mentioned above is used tounlock the stanchion from the railroad car before the repositioning stepand lock the stanchion after the repositioning step. Apparatus on thetractor activates a hook to hook a portion of the stanchion to thetractor before the raising step and to unhook the stanchion from thetractor after the raising step.

The method of unloading a trailer secured to a railroad car by astanchion using a tractor includes positioning the tractor adjacent tothe trailer and the stanchion. Next, the tractor disconnects the trailerfrom the stanchion and connects the trailer to the tractor. The tractorrepositions the trailer and the stanchion to a desired position in whichthe stanchion is to be stowed, and finally removes the trailer from therailroad car.

The tractor disconnects the trailer from the stanchion by lowering thestanchion. The tractor unlocks the stanchion from the railroad car byapplying an unlocking force before the repositioning step and relocksthe stanchion to the railroad car after the repositioning step. A hookon the tractor engages the stanchion after it is unlocked and pulls itto its repositioned position and then unhooks from the stanchion beforeremoving the trailer. The stanchion is repositioned to one end of therailroad car to be ready for the next loading operation.

Thus, the unique stanchion and its manipulation by the tractor allowsthe stanchion to be repositioned during loading and unloading, in orderto secure the most efficient use of deck space on the train, as well asbeing raised and lowered. Similarly, all the operations, repositioningand controlling of the stanchion are performed from the tractor, therebyreducing the amount of time, the number of steps and the number ofpeople involved in the loading and unloading of the trailer and thepositioning and repositioning of the stanchion.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-5 are schematic representations illustrating a method of loadinga trailer on a railroad car according to the principles of the presentinvention.

FIGS. 6-9 are schematic representations of the method of unloading atrailer from a railroad car according to the principles of the presentinvention.

FIG. 10 is a partial view of a modification for the hook positioningmechanism;

FIG. 11 is a partial cut-away side view of a hook according to theprinciples of the present invention in its set position;

FIG. 12 is a partial cut-away side view in its released position;

FIG. 13 is a plan view with partial cut-aways of a stanchion accordingto the present invention.

FIG. 14 is a partial cut-away front view of the stanchion of FIG. 10.

FIGS. 15A, 15B, and 15C are schematic views of a modification of thehook mechanism according to the principles of the present invention in aretracted, extended and lowered, and extended and raised positions.

FIG. 16 is a partial plan view with partial cutaways of a stanchionaccording to the principles of the present invention.

FIG. 17 is a partial cross-section view of the stanchion of FIG. 16.

FIG. 18 is a schematic presentation of the interlocking mechanism withthe stand in its lowered position and the latch in its locked condition.

FIG. 19 is a schematic view of the interlock mechanism with the stand inits lowered position and the latch mechanism in its unlocked condition.

FIG. 20 is a schematic view of the interlock mechanism with the stand itits raised position and the latch in its locked condition.

FIG. 21 is a schematic view of the interlock mechanism with the stand intransition between its raised and lowered position and the latch in itslocked condition.

FIG. 22 is a schematic view of a shock absorber connection of the hook.

DISCLOSURE OF THE INVENTION

The present system as illustrated in FIGS. 1-9 includes a tractor 10connected to or to be connected to a trailer 12, which is to bepositioned along a surface 14 of railroad cars 16. A stanchion 18 ismounted on the railroad car 16 to support the trailer 12 and secure itto the railroad car 16. The stanchion 18 includes a slide frame 20 whichslides along a rail 22 in the individual cars 16 and a stand 26pivotally mounted to the slide 20. The rails 22 include a plurality ofapertures 24 to receive a latch mechanism which is released by externalforce applied to plunger 28. A fifth wheel connection 30 is on the stand26, as is the standard release mechanism 32. A pair of cars 16 are shownwith the stanchion 18 at one end of the car frame 16A of the right car.The details of the latch mechanism and the stanchion 18 will bedescribed with respect to FIGS. 10 and 11.

The tractor 10 is shown with the closest wheel removed to expose theadditional mechanism applied thereto according to the present invention.A gate 34 which applies external force to the plunger 28 of the latchmechanism of the stanchion 18 is pivotally mounted to tractor 10 and iscontrolled by fluid device or motor 36. In FIG. 1, the gate 34 is shownin its raised or locking position, and in FIG. 2 in its loweredunlocking or position. Also pivotally mounted to the tractor 10 is ahook 38 controlled by fluid device or motor 40 to be in its raised orunhooking position of FIG. 1, or its lower and hooking position of FIG.2. The tractor 10 also includes a fifth wheel connection 42 to receivethe king pin 44 of the trailer shown in FIG. 4.

The loading process begins, as illustrated in FIG. 1, with the stanchion18 at one end 16A of a car 16 and the plunger 28 extended under springbiasing such that the latch mechanism is in its locked position. Trailer12 is backed onto the car 16 by a tractor 10. The gate 34 is up in itslocking position and the hook 38 is also up in its unhooking position.Trailer 12 is backed onto the decks of the cars 16 and over the droppedor lowered stanchions 18 until the platform on which the desiredstanchion is located is reached.

Upon approaching the desired stanchion 18, the operator lowers the gate34 by fluid motor 36 to its down position as illustrated in FIG. 2. Thetractor 10 continues to back up the trailer 12 until the gate 34 engagesthe plunger 28, overcoming the spring bias of the latch and unlockingthe stanchion 18. The continued rearward movement of the tractor 10moves the trailer 12 and repositions the stanchion 18 through forceapplied by gate 34 to the desired location along the deck 14 of the car16. The operator also lowers the hook 38 using fluid motor 40 inpreparation for later use.

Since the latching mechanism is in its lock position, the initialpressure applied by gate 34 to the plunger 28 moves the plunger relativeto the sled. As the latch unlatches, the friction between the sled 20and the surface of the car and the rails generally prevents movement ofthe sled relative to the railroad car and thereby maintains the latch inits unlocked position. Thus the biasing of the spring is generally lessthan the friction force. To further assure that the latch mechanism willunlatch or unlock the stanchion 18, the lowered hook 38 is caused to liein an opening in the frame of the stand 26 which includes a bar. Forwardmovement of the hook relative to the stanchion will cause the hook 38 toengage the bar. This may be by hydraulics or by forward movement of thetractor 10. Once hook 38 engages the stanchion, the gate 34 is loweredto engage the plunger 28 and drive it back against the spring bias tounlock the latch. Thus the stanchion 18 and the plunger 28 are securedbetween the hook 38 and the gate 34. This not only assures unlatching orunlocking of the stanchion 18, but maintains this unlatched position foreither direction of travel of the tractor 10. The distance between thehook 38 and the lowered gate 34 is selected to be substantially equal tothe distance between the bar on the stand 26 and the contracted plunger28.

When the desired position on the surface 14 of car 16 is reached, theoperator raises gate 34 from its lowered or unlocking position to itsraised position or locking position. Plunger 28 is then extended and thestanchion 18 is latched or locked into place at a specific positionalong the surface 14 of car 16. The extended plunger 28 is illustratedin FIG. 3. The operator then sets the trailer brakes, releases the kingpin from the fifth wheel connection 42, and moves the tractor forward.

Since the hook 38 lies in an opening in the frame of the stand 26 whichincludes a bar, and the stanchion 18 is latched or locked to the rail22, the forward movement of the tractor 10 causes the hook 38 to engagethe bar and raises the stand 24. Simultaneously, the king pin 44 of thetrailer 12 slides out of the tractor fifth wheel connection 42 asillustrated in FIG. 4. As the tractor 10 continues to move forward, thetrailer 12 begins to shift from the fifth wheel connection 42 of thetractor 10 to the stanchion 18 fifth wheel connection 30. The fifthwheel connection 30 of the stanchion continues forward relative to thetrailer 12 as a result of the pivoting of the stand 26. The hookadjustment is such that the release trigger 32 is not depressed at thefull up position unless the tractor 10 is backed up by the operator.

With continued forward movement of the tractor 10, as illustrated inFIG. 5, all the weight of the trailer 10 is now on the upright stanchion26. Vertical member 46 is upright and the diagonal brace members 48 and50 are locked to each other. The operator on the tractor 10 then raisesthe hook 38, disengaging it from the vertical member 46. To be certainthat the king pin 42 of the trailer 12 is engaged by the fifth wheelconnection 30 of the stanchion, the tractor is pulled forward and itsfifth wheel connection 42 is raised. Tractor 10 is then backed againsttrailer 12 to push the king pin 44 home into the fifth wheel connection30 of the stanchion 18. This completes the loading and securing of thetrailer 12 to the car 16.

The unloading operation begins by backing up the tractor 10 until it isadjacent to the stanchion 18 and under the trailer 12. As the back ofthe tractor 10 engages trigger 32, it depresses it, releasing both thediagonal brace members 48 and 50 and the trailer king pin 44 and fifthwheels 30 latch. With this continued movement as illustrated in FIG. 6,the stanchion 18 collapses with the weight shifting from the fifth wheelconnection 30 of the stanchion 18 to the fifth wheel connection 42 ofthe tractor 10. The latch mechanism of the stanchion 18 is in its lockedposition, allowing this to occur. Similarly, the gate 34 and the hook 38on the tractor 10 are in their raised positions. Tractor 10 continuesbackwards, and the trailer king pin 44 couples to the tractor fifthwheel connection 42 of the tractor 10. The driver then connects thebrake hoses of the tractor 10 to the trailer 12 and releases the trailerbrakes. Stanchion 18 is in its completely collapsed position asillustrated in FIG. 7.

To reposition the stanchion 18 at the front end 16A of car 16, theoperator activates fluid motor 40 to drop the hook 38 to its loweredposition to hook the stanchion 18. This is illustrated in FIG. 7. Next,the operator activates the fluid motor 36 to lower the gate 34 todepress the plunger 28 to unlock the latch mechanism of the stanchion18. With the plunger 8 and stanchion 18 secure between hook 38 and gate34 the stanchion 18 moves forward or backward with the trailer 12 andthe tractor 10 when it moves forward along the deck as illustrated inFIG. 8. At the end of the deck 16A, the operator raises the hook 38using fluid motor 40 and rotates the gate 34 up using fluid motor 36.The latch mechanism being biased, will then move to its locked positionlocking the stanchion 18 to the railroad car 16. This allows the tractor10 and trailer 12 to move off the railroad car, while leaving thestanchion 18 properly positioned for loading as illustrated in FIG. 9.

As can be seen from the method of the loading and unloading of FIGS.1-9, the interaction between the tractor 10 and the stanchion 18 allowsthe stanchion to be positioned and repositioned with the loading andunloading of the trailer 12, as well as being raised and lowered in itsappropriate position. This is all accomplished from the tractor 10 by asingle operator. Also, the stanchion 18 and the trailers 12 may bepositioned anywhere along the surface of the car 16. This allows closerpositioning of the trailers relative to each other, thereby reducingwind resistance and making more efficient loading.

To prevent any forward movement of the stanchion 18 from beingtranslated into a lifting or rising motion of the stand 26, a mechanismis provided in FIG. 10 to change the center line of the hook 38. Inaddition to fluid motor 40, a second fluid motor 41 is provided andconnected to the pivot point A of the arm of the hook 38. The arm 37 hashook 38 thereon. The fluid motor 41 shifts the pivot point 43 fromposition A down to position B in slot 39 to thereby lower the angle thatthe arm of the hook 38 makes with the direction of motion. This wouldsubstantially reduce the lifting force on the stand 26 during a slidingmotion of the sled 20.

To more accurately control the operation of the hook 38, a modificationis illustrated in FIGS. 11 and 12. Hook 38 is pivotally connected at 31to the hook arm 37. A stop 33 is provided on the hook arm 37 and engagessurface C of the hook 38 in its hooking position as illustrated in FIG.11 or engages surface D in its unhooked or release position as in FIG.12. A torsion spring 35 biases the hook 38 to its set or hookingposition as illustrated in FIG. 11 with a surface C engaging the stop33. A fluid motor 45 forms part of or is connected to the hook arm 37and includes a plunger 47 having one end extending out towards the hook38. Spring 49 within the fluid motor 45 biases the plunger 47 to itsextended position. Upon fluid actuation, the piston 47 retracts againstthe spring 49 and retracts the piston 47. In its extended position asillustrated in FIG. 11, the piston 47 engages an axis of stop forsurface D of the hook 38 and locks it in its hooked or set position.When it is desired to release the hook, fluid pressure retracts theplunger 47 causing it to disengage surface D of the hook 38. Forcesapplied to the hook 38 to the right in FIGS. 11 and 12 will cause thehook to rotate against the spring 37 and move to a release or unhookingposition. These forces are generally a forward movement of the hookrelative to the stanchion 18. Once this pressure is released, the spring35 returns the hook to the hooking position illustrated in FIG. 11. Oncethe fluid pressure in the motor 45 is released, the spring 49 forces thepiston 47 to extend and engage the hook 38. Once the force on the hook38 is removed, spring 35 pivots hook 38 to the position at FIG. 11 asspring 49 drives the piston 47 into its engaging lock position againstsurface D of the hook 38. If it is desired to have the hook 38 continueto rotate clockwise from its lock position in FIG. 11 to aid inplacement, the stop 33 would be removed. This may be desirable when thehook arm 37 has dropped and the hook is sliding across the stanchion 18.

To more accurately control the position of the hook when the stand israised, an articulated modification is illustrated in FIGS. 15A, 15B,and 15C. Hook arm 37 has a first link 37A pivotally connected to thetractor 10 by a shaft 51 and a second link 37B including the hook 38pivotally connected to the first link at 37C. Although the hookstructure of FIGS. 11 and 12 are included as the preferred embodiment, arigid hook may be used if desired. A third link 53 is pivotallyconnected to the second link 37B at 55 and is connected to the tractor10 by a pin 57 extending into slot 59 of the third link 53. An operatoror fluid motor equivalent to 41 will control the position of the hook byrotating shaft 51. This interconnection is well known and has beendeleted from the figures for sake of clarity.

The hook in its retracted position is illustrated in FIG. 15A whereinthe operator controls the link 37A to be in its substantially verticalposition. This will cause link 37B to be in its retracted position ascontrolled by link 53. To extend the hook to the position in FIG. 15B,shaft 51 is rotated counter-clockwise until the links 37A and 37B arecoaxial. The pin 57 lies in the uppermost portion of the slot 59 in link53. The position in FIG. 15B may be obtained merely by releasing thebiasing force on shaft 51 and allowing gravity to move the link 37Bdownward.

Any upward movement of the extended hook is accommodated by the slot 59in the link 53. These forces may be by the rising of the stand to theposition illustrated in FIG. 15C. The pin 57 is shown in the lower endof the slot 59. This raising of the hook from the position of FIG. 15Bto that of 15C does not affect the colinearity of the hook links 37A and37B.

To retract the hook 37 from the position in FIGS. 15B or 15C, the shaft51 is rotated clockwise until it reaches the position of FIG. 15A. FIGS.15A-15C are schematic representations to aid in the understanding of thelocation of the elements. Since the third link 53 is always undertension, it may be replaced with a cable.

To accommodate large forces external on the hook mechanism 37, 38, ashock absorbing system is illustrated in FIG. 22. The links 37A and 53are connected to a block 131 slidably mounted to the tractor 10. Aspring 134 and roller 136 are connected to the tractor and ride on aramp 132 on the sliding block 131.

The stanchion 18 according to the present invention is illustrated inFIGS. 13 and 14. Since the stand 26, the fifth wheel connection 30 andthe release mechanism 32 are well known prior art structures, they willnot be described and illustrated in detail. The improvement of thepresent invention is the specific latching mechanism to lock the frameor sled 20 of the stanchion 18 to the railroad car 16. This is used incombination with the rail 20 having apertures 24 and the operableelements 34 and 38 on the tractor 10.

The sled 20 includes a rectangular frame having guides 52, 54, 56 and 58at its four corners. Pivotally connected to the guides 52 and 54 is thevertical stand member 46. Pivotally connected to the guides 56 and 58 isone of the diagonal struts 50. As illustrated in FIG. 14, each of theguides 52, 54, 56 and 58 includes a channel 60 for receiving thehorizontal portion of the rail 22. A vertical portion of the rail 22extends down and out of the channel 60 and is secured to the frame ofthe car 16. The rail 22 and channel 60 position the stanchion 18 in arecess 64 in surface 14 of car 16. The wheels of the trailer 12 and thetractor 10 lie on either side of the protective wall 66 of the recess64.

A bar 70 lies in an opening 72 of plate 74 which is secured to thevertical members 46 of the stand 26. The hook 38 engages the bar 70 inraising the stanchion during loading, and in repositioning the stanchionduring unloading operations as previously described.

The latch mechanism includes the release plunger 28 which extendsthrough a collar 80 which is secured to a face plate 82 of the sledframe. A yoke 84 is secured to the other end of the plunger 28 byfasteners 86. A spring 88 engages, at one end, the yoke 84 and, at itsother end, a spring stop 118 which is secured to plate 92 of the frame.The spring 88 biases the plunger 28 to its extended or locked position.A pair of links 94 pivotally connected at 96 to the yoke 84 at one endand to an upper arm 98 of a dog at 100 at its other end. The upper arm98 of the dog is connected by shaft 102 to the lower end of the dog 106through a journal 104 in the guide 54. The end of dog 106 engages theapertures 24 in the rail 22 to lock the stanchion to the rail in itssolid position. When the plunger 28 is retracted by the application ofan external force, the yoke 84 moves the link 94 and the upper arm 98and dog 106 to its retracted or unlocked position as illustrated inphantom in FIG. 13.

It should be noted that the relationship of links 94, yoke 84 and upperarm 98 are designed such that any forces on the dog 106 are appliedalong the axis of the links 94 which extends between the pivot points96, 100. These forces along this axis thereby do not transmit forces tothe plunger 28, and therefore will prevent unlocking of the dog 106 byforces applied to the dog. These forces may result from the attemptedshifting of the trailer on the railroad car or any of the forces appliedto the sled 20.

Although only one dog 106 is shown in FIG. 13, a second dog is underplate 74. As illustrated in FIG. 14, the second dog 106 engages anaperture 24 in the rail 22 in the vertical portion of the rail 22 belowthe horizontal portion.

A modification to the latch system is illustrated in FIGS. 16 and 17.Instead of the plunger 28 being connected directly to the yoke 84, theplunger 28 is connected through links 110, 112, 114, and plate 116 tothe yoke 84. The yoke 84 rides along rail 83 around which is wound thebiasing spring 88 which biases the yoke 84 to the dog extended orlatches' locked position. A single link 118 connects the yoke 84 to thedog 106. In their locked position, the single links 118 connecting theyoke 84 to the dogs 106 are coaxial. This provides a more stable lockingposition for the dogs and any force which attempts to unlock the dogs,when in use other than the force applied from the plunger 28 to thelinkage, will be transferred between the dogs and prevent them fromunlocking.

It should be noted that in the top half of FIG. 16, the plunger 28 is inits extended position with the latch or dogs in their extended or lockedposition and in the lower half of FIG. 16, the plunger 28 is in itsretracted position and the dog or latch is in their retracted orunlocked position.

Link 112 is secured to a rotary shaft 120 rotatably connected to thesled. Also connected to the rotary shaft 120 is the interlock system.The interlock system prevents the stand from being raised when the dogsare in their locked position. If the stand is in its raised position,the interlock prevents the dogs from unlocking. The interlock system isillustrated in FIGS. 16-21. It includes a cam follower 124 mounted toflange 122 connected to each of the front legs 46 of the stand and alsoincludes a pair of cams 126 connected to the shaft 120 to rotatetherewith. The cam 126 includes a camming surface 128 and a secondsurface 130.

When the stand is in its lowered position and the latch or the dogs 106are in their locked position as in FIG. 16, top half, and FIGS. 17 and18, the cam surface 128 is generally horizontal and spaced from the camfollower 124. Thus, the stand can move from its lowered position of FIG.18 to its raised position in FIG. 20. Forces applied to plunger 28 tounlock the dogs 106, illustrated in the lower half of FIGS. 16 and 19,rotates via links 110 and 112 the shaft 120 clockwise in FIGS. 17-21.This positions the camming surface 128 into engagement with the camfollower 124 as illustrated in FIG. 19. This engagement prevents thestand from rising. Any attempt to rise the stand will causecounter-clockwise rotation of the cam 126 which will immediately drivethe dogs 106 into their extended or locked position. The design of thelinkage of FIGS. 16 and 17 is such that if the stand is in any positionother than substantially horizontal or lowered, the dogs 106 will beextended sufficiently to have a locking condition.

With the latch or dogs in their locking position, the surface 128 ishorizontal. When the stand 46 is in its raised position, the cammingsurface 128 engages the cam follower 124 as illustrated in FIG. 20. Therelative position of the camming surface 128 and the cam follower 124with the stand in transition between its raised and lowered position andthe dogs being locked is illustrated in FIG. 21. It should also be notedthat with the stand in its raised position and being locked in itsraised position by other mechanisms, the dogs 106 cannot be releasedbecause of the interlock mechanism. Any attempt to unlock the dogs wouldcause clockwise rotation of cam 126. This motion would be stopped by thelocked leg 46 of the stand.

Thus, it can be seen that the interlock system prevents the stand frombeing raised when the dogs are unlocked as in FIG. 18 as well aspreventing the dogs from being unlocked when the stand is raised, asillustrated in FIG. 20. Even if the stand 46 did not have its ownlocking mechanism, the weight of the trailer on the leg 46 would providesufficient force to prevent clockwise rotation of cam 126 to unlock thedogs. Assuming a force was accidentally applied in an attempt to unlockdogs in the partially raised position of FIG. 21, the cam 126 willrotate clockwise and come into engagement with the cam follower 124.Since it does not rotate a full 90 degrees, for example, the dogs willbe moved but will not fully disengage from the locked position in slots24 of the rail 22. It should be noted that 90 degrees is only an exampleof the amount of rotation travel on a linkage system. The linkage systemshould be designed such that the dogs disengage only after a substantialportion of travel is completed.

The unique latch mechanism and its cooperation with the gate and hook onthe tractor provides the versatility of the present system. Thus, acomplete operation and methods of loading and unloading can be conductedby a single operator of the tractor. Other than dismounting from thetractor to connect and disconnect the brake systems of the tractor 10and the trailer 12, the operator can load and unload the trailer 12 aswell as position, reposition, raise and lower the stanchion 18 all fromthe cabin of the tractor 10.

Although the present invention has been described and illustrated indetail, it is to be clearly understood that the same is by way ofillustration and example only, and is not to be taken by way oflimitation. The spirit and scope of the present invention are to belimited only by the terms of the appended claims.

What is claimed:
 1. A system for positioning and supporting trailers onstands on a railroad car with a tractor, including hook means on saidtractor for engaging said stand means when said tractor is adjacent saidsled means, said hook means comprising:a first link pivotally connectedto said tractor at a first end; a second link having a hook on a firstend and pivotally connected at a second-end to said first link;, hookextender means for moving said first and second links between extendedand retracted positions; a hook member pivotally connected to saidsecond link to form a hook configuration therewith; and lock meanshaving a first position for locking said second link and said hookmember in said hook configuration and a second position for allowingsaid hook member to rotate relative to said second link.
 2. A systemaccording to claim 1 wherein said hook includes biasing means forbiasing said second link and said hook member into said hookconfiguration.
 3. A system for positioning and supporting trailers onstands on a railroad car with a tractor, including hook means on saidtractor for engaging said stand means when said tractor is adjacent saidsled means, said hook means comprising:a first link pivotally connectedto said tractor at a first end; a second link having a hook on a firstend and pivotally connected at a second-end to said first link; and hookextender means for moving said first and second links between extendedand retracted positions in response to pivotal motion of said first linkat its first end.
 4. A system according to claim 3 wherein said hookextender means includes a third link connected between said tractor andsaid second link.
 5. A system according to claim 3 wherein said hookextender means includes a cable connected between said tractor and saidsecond link.
 6. A system for positioning and supporting trailers onstands on a railroad car with a tractor, including hook means on saidtractor for engaging said stand means when said tractor is adjacent saidsled means, said hook means comprising:a first and second memberpivotally connected to form a hook configuration with said first membertransverse to said second member; and lock means having a first positionfor locking said first and second members in said hook configuration anda second position for allowing said first and second member to rotaterelative to each other into and out of said hook configuration.
 7. Asystem according to claim 6 wherein said hook means includes biasingmeans for biasing said first and second members into said hookconfiguration.
 8. A system according to claim 6 wherein said lock meansincludes a fluid motor for operating said lock means.